The invention relates to a measuring arrangement for autoclaves or similar devices under heavy climatic conditions, comprising at least one measuring probe for detecting physical quantities to be measured, e.g., a temperature measuring probe, a measuring electronics connected or adapted to be connected with the measuring probe via a connection line and arranged in a thermally insulated container, which measuring electronics includes a transmitter unit to which a transmitting antenna is associated, which is arranged outside of the container on a lid provided therefor and is connected or adapted to be connected via a connection line, and a separate receiver unit to which a receiving antenna is associated.
In measuring technology, there are often situations where given measuring quantities, such as temperature, pressure, etc., are to be detected under difficult or critical conditions, such as, for instance, under vapor atmosphere, in hot-water sterilizing apparatus, or, in general, at elevated temperatures, elevated pressures and the like. Typical example are vapor sterilizers or sterilizing autoclaves, as they are used, for instance, in the food industry or in the pharmaceutical industry in order to sterilize food, infusions, solutions and the like products by means of water vapor at an elevated temperature and an elevated pressure. Primarily in the pharmaceutical industry, highly precise temperature measurements on several sites within the autoclave are required for the validation and process control of the sterilizing process. With stationary autoclaves, temperature probes usually are introduced into the autoclaves via leadthroughs. However, with rotating autoclaves, such a technique is not applicable. Thus, with conventional apparatus for rotating autoclaves the measured values are stored during the sterilizing treatment, the apparatus being ready for inquiry on the progression of sterilization only after completion of sterilization and unable to transmit measured values during the treatment process, for instance, in order to enable prompt reaction on changing sterilization conditions.
Such measured value storing in an electronic storage device within a temperature-insulated container is described in DE-C-23 08 887, for instance, in connection with the sterilization of tins, with a measuring electronics largely free of errors being sought, in particular. Such storing of measured values, such as temperature values, during a treatment procedure might be acceptable in the sterilization of tins, because there the sterilization treatment is not that crucial and repetition of the sterilization treatment is necessary only rarely, if required on grounds of the subsequent evaluation of the measured values stored. This is completely different with the abovementioned pharmaceutical products, with which a sterilizing temperature must be observerd over a defined period of time with great accuracy in order to safeguard sterilization to the desired extent. If, in that case, a deviation of the sterilizing temperature during a defined period of time, based on the measured values stored, is detected only afterwards, the sterilizing procedure must be repeated for these products, which, in practice, involves high expenditures in terms of time and money on account of several treatment repetitions. Therefore, in practice, a comparatively long sterilization time is provided from the very beginning for reasons of safety, treatment repetitions, thus, proving necessary only rarely; however, this involves the disadvantage of a comparatively long sterilization time being generally required.
On the other hand, the problem of an adequate thermal insulation in case of such sealed measured-value storing containers can be solved more readily than in those cases where the external transmission of measured values is constantly required. This is due not only to the fact that the connections to the measuring probes are to be made tight, but also that it is easier to keep the electronics in a thermally insulated container, thus also requiring comparatively little space. Hence it is possible to accommodate the measuring electronics plus storage and battery within the container having given external dimensions even with a highly complex insulation. If, however, the circuitry has to be extended for the transmission of the measured values, this involves a larger space demand within the container, the thermal insulation thus having to be designed less complex at given external dimensions of the container. On the other hand, enlargement of the container is not possible in most cases, because the space provided for such containers in autoclave charging cars usually is very limited. Apart from this, there will be an increased demand for insulation going hand in hand with an increased external surface on grounds of the thus increased heat transfer surface, a noticeable gain of space being feasible only with relatively extensive container dimensions.
Special temperature protection vessels for measuring means, furthermore, can be taken from DE-C-25 09 787 as well as from DE-A-27 20 118, which, however, are very complex in construction on account of incorporated water reservoirs. Moreover, a temperature protection vessel for a battery operated measured value circuit memory is described in DE-C-35 45 215, wherein it is considered advantageous that, due to the storage of the measured values in the electronic memory circuit, the otherwise necessary trailing cable connection to a display station and a high-frequency signal transmission from the furnace during the furnace campaign of the open-ended furnace car can be obviated. As pointed out, such measured value storage results in a simplified structure and circuitry, yet it involves the disadvantages of frequently repeated heat treatments in case of critical products, in particular, sterilization treatments in case of pharmaceutical products.
In connection with vapor sterilizers, measured data transmission from the sterilizer by radiotelegraphy was generally proposed in AT-B-388 502. As a temperature protection container, a metallic double-shell container is proposed, the cavity between the shells having to be evacuated and filled with celite. The measuring electronics is cast into paraffin together with the transmitter circuit in the interior of this container and is connected with the individual measuring probes via electrically insulating leadthroughs provided in the lid of the metallic container. In fact, this known measuring arrangement has never been successful in practice, and experiments carried out with similar measuring arrangements, which have led to the present invention, have proved that only insufficient functioning can be attained with measuring arrangements of this kind. In detail, an inadequate thermal insulation of the measuring electronics within the metallic container and hence errors in the measured value transmission result in addition to the fact that also the conduit leadthrough in the lid of the container cannot be made sufficiently tight and is cumbersome in handling. In total, only extremely short operation times are obtained with the known measuring arrangement, i.e., the known measuring arrangement each can be employed only for a rather short sterilization procedure. After this, the container must be replaced with a new one, because too high an internal temperature has already prevailed in the previously used container. In addition, the circuit calls for recharging of the used batteries after a relatively short time. In practice, these disadvantages apparently have led to the sustained use of measuring arrangements based on measured value storage as discussed above in vapor sterilizers.
Furthermore, it is also known, for monitoring the temperature of rotating machine parts, such as, for instance, heating rolls or rotors of electric equipment, to transmit the temperature data to a stationary means in a wireless manner. To this end, light-emitting diodes (LEDs) in connection with modulated light radiation may be used, cf. e.g., EP-B-75 620 and DE-A28 52 679, or capacitive transmission by means of a capacitor, one plate of which co-rotates with the rotating part of the machine and whose counter-plate is stationarily arranged , cf. e.g., DE-C-24 28 890. However, such transmission means for the wireless transmission of measured values obviously are not or not readily applicable to vapor sterilizers or autoclaves, primarily because the light transmission by aid of LEDs would, for instance, be impeded by the vapor present and the LEDs could hardly be thermally insulated to a sufficient extent at such elevated temperatures. Similarly, the capacitive transmission would be falsified by the vapor present between the capacitor plates.